Don't feel bad I had my gauges in and out 3-4 times after everything was painted up. Really sucks pulling it all back out again.

I learned it best to test all the gauges with a 9v battery, a couple alligator clips and a 100 ohm POT. (Not the AMP gauge though you will burn it up)

I found it easiest to test my fuel gauge starting at the wire in the trunk. There is a plug under the trunk latch with two wires. One is for the lamp for the licenses plate and the other to the gas sending unit.

Hope I remember this right but with the key on you should have 12V on the wire. With it pulled the needle of the gas gauge will swing all the way Full and with the wire grounded it will swing all the way empty or maybe its the other way around. Its a good place to start.